1. Field of the Invention
This invention relates to fungicidal compositions comprising particular concentrations of three saponins extracted from Capsicum spp. The invention further relates to methods for using the antifungal compositions for improving crop resistance to fungi, including aflatoxin-producing fungi, and for treating animals and human patients for fungal-induced conditions and disease.
2. Description of the Relevant Art
Archeological evidence indicates that peppers belonging to the genus Capsicum were domestically used by Mesoamerican cultures at least 6100 years ago and predates pottery in some regions (Perry et al. 2007. Science 315: 986-988). Historically, these peppers were used by the native peoples of Mesoamerica in food flavoring (Molina-Torres et al. 1999. J. Ethnopharm. 64: 241-248). They still constitute an important component of the Mexican diet. In addition to food flavoring, various parts of these plants were also used as medicinal agents by the Mesoamerican peoples. Capsicum spp. produce a number of capsaicinoids, with capsaicin being the main capsaicinoid produced by these plants. It stimulates sensory afferent neurons (Buck and Burks. 1986. Pharm. Rev. 38:179-226; Caterina et al. 1997. Nature 398:816-824). Capsaicin also inhibits bacterial growth and causes platelet aggregation (Caceres et al. 1991. J. Ethnopharm. 31:193-208; Molina-Torres, supra; Wang et al. 1984. Thrombosis Res. 36:497-507; Sylvester and LaHann. 1989. Proc. Western Pharm. Soc. 32:95-100; Hogaboam and Wallace. 1991. Eur. J. Pharm. 202:129-131). Capsaicin also causes membrane fluidity changes at concentrations corresponding to antibacterial and anti-platelet concentrations (Tsuchiya, H. 2001. J. Ethnopharm. 75:295-299).
Capsicum spp. also produce saponins, which are amphiphilic compounds having detergent-like properties and commonly found in plants. In vivo, saponins bind to cholesterol and bile acids and reduce the presence of these compounds in the blood of animals (Cho et al. 2006. Eur. J. Pharm. 550:173-179; Li et al. 2008. Phytotherapy Res. 22:159-164; Son et al. 2007. Biosci. Biotech. Biochem. 71:3063-3071). Much less is known of Capsicum spp. saponins than capsaicinoids present in these plants. CAY-1 (FIG. 1), a steroidal saponin present in cayenne pepper and paprika, has potent fungicidal properties against a number of fungi of agricultural and medical importance (De Lucca et al. 2002. Med. Mycology 40:131-137; De Lucca et al. 2008. Am. J. Enol. Viticult. 59:67-72, Renault et al. 2003. Med. Mycology 41:1-7; Stergiopoulou et al. 2008. Med. Mycology 46:1-7; Yajima et al. 2000. Food Sci. Tech. Res. 6:99-101). CAY-1, in vitro, has shown additive synergy with Amphotericin B and intraconazole against Aspergillus flavus, A. fumigatus and A. niger (De Lucca et al. 2006a. Chemotherapy 52:285-287).
However, other Capsicum spp. saponins are not as active. For example, the saponins 1081 and 919 (FIG. 1) closely elute with and are close structural relatives of CAY-1; however, saponin 1081 is poorly antifungal, while 919 has no antifungal properties (De Lucca et al. 2006b. Canadian J. Microbiol. 52:336-342). They lack one and two glucose moieties, respectively, present in CAY-1. No additional information concerning these saponins is known. In planta, CAY-1, 1081 and 919, in a weight-to-weight-to weight measurement, exist in a ratio of 4:3:3 (data not published).
While the anti-fungal properties of the saponins CAY-1, 1081, and 919 in pure form are known in the art, there still remains a need in agriculture for effective fungicidal compositions for reducing fungal and aflatoxin contamination of crops and for pharmaceutical anti-fungal compositions for treating animals for fungal-induced diseases and conditions. The present invention, described below, provides potent fungicidal compositions comprising CAY-1 (at suboptimal concentrations) together with 1091 and 919 and methods of using these compositions to effectively reduce fungal contamination of crops and to treat animals and humans having fungal-induced diseases and conditions.